Dimethylformamide (DMF) is an important commercial commodity of extensive technical uses, particularly as a solvent for certain plastic coatings and films, a solvent for certain gases, dyes and electrolytes, a cleaner and paint remover, etc. The most commonly used processes for the production of DMF are (1) the one stage catalytic reaction of carbon monoxide and dimethylamine and (2) the two stage catalytic process wherein carbon monoxide is first reacted with methyl alcohol to produce methyl formate and the latter reacted with dimethylamine to obtain DMF.
As described by Kirk-Othmer: Encyclopedia of Chemical Technology 3rd edition (1980) vol. 11, pages 264-265, in the one stage process a solution of dimethylamine in methanol is reacted with carbon monoxide in the presence of catalyst such as sodium methylate or metal carbonyls, at 110.degree.-150.degree. C. and at pressure of 1.5-2.5 MPa (about 220-365 psi). In the two-stage process carbon monoxide and methanol are reacted in the presence of sodium methylate, at high pressure and at temperature of 60.degree.-100.degree. C., to obtain methyl formate which latter is recovered by distillation and then reacted with dimethylamine at 80.degree.-100.degree. C. and at low pressure.
Numerous other processes for the production of DMF are disclosed in prior patents. Typically among the more recent patents particularly concerned with the production of DMF, are the following:
U.S. Pat. No. 4,218,398 in which a mixture of alkylamines is reacted with carbon monoxide in the presence of a halogen-containing catalyst. PA1 U.S. Pat. No. 4,224,243 in which a mixture of alkylamines, which may also contain monomethylformamide (MMF), is reacted with CO in the presence of hydrogen, over iron catalyst. PA1 U.S. Pat. No. 4,230,636 wherein a mixture of alkylamines is reacted with carbon monoxide over iron catalyst. PA1 U.S. Pat. No. 4,251,460 in which a mixture of di- and trimethylamines is reacted with CO. The said mixture of amines is obtained by reaction of methanol and ammonia in the presence of dehydration catalyst and removing resulting monomethylamine from the reaction mixture. PA1 U.S. Pat. No. 4,269,998 in which a dialkylamine is reacted with CO.sub.2 and water over copper chromite catalyst. PA1 U.S. Pat. No. 4,302,598 wherein dimethylamine is reacted with CO in the presence of alkali metal methylate catalyst; excess of dimethylamine permits recycling and reuse of the catalyst.
Among earlier patents of interest, U.S. Pat. No. 3,412,151 discloses production of DMF by reaction of trimethylamine with water and CO.sub.2 in the presence of dicobalt octacarbonyl catalyst at CO pressure in the range of 1000 to 6000 psig.
U.S. Pat. No. 4,244,889 is directed to the preparation of acetamides from CO, H.sub.2 and a nitrogen-containing compound (ammonia or nitric oxide) over a solid catalyst comprising rhodium and manganese. Using ammonia as reactant and operating at a total pressure of 1000 psig, the obtained product is reported to contain principally about 31% methane, about 30% acetamides and about 14% acetic acid; among the remaining products there was included about 7.6% N,N-diethylformamide.
Other patents disclosing the use of rhodium and/or ruthenium catalyst in production of N-substituted formamides by reaction of an amine and an oxide of carbon include U.S. Pat. Nos. 3,099,689 and 3,530,182. U.S. Pat. No. 4,292,242 discloses the use of a mixed ruthenium carbonyl/iron carbonyl catalyst in aminomethylation by reaction of an olefin with an amine or ammonia in the presence of CO and hydrogen, wherein the catalyst is dissolved in a suitable solvent, among which are listed various alcohols, glycols, DMF, sulfolane, etc.
U.S. Pat. No. 4,250,116 is concerned with the production of methyl and ethyl amines by reaction of carbon monoxide and hydrogen with ammonia (or nitric acid) over heterogenous solid catalyst comprising rhodium and iron. The reaction product obtained is reported to contain about 38% of alkalamine, about 22% methane, about 27% alcohols and less than about 2% DMF; there is no report of the presence of MMF or unsubstituted formamide.
Published Japanese patent application Sho57-42660, is concerned with the manufacture of formamides by reaction of ammonia or an amine with carbon monoxide over rhodium oxide or other platinum group catalysts listed. With alkylamine as starting reactant the principal reaction product is the formamide corresponding to the particular alkylamine used.